Method of preparing zein solutions directly from gluten



Patented Sept. Z6, 1944 uNl'raD STATES PATENT (OFFICE.

- METHOD or PREPARING zam SOLUTIONS nmno'rnr mom GLUTEN Roy. E..Coieman, Chicago, 111., assignor to Time,

Incorporated, a corporation of New York No Drawing. Original application November 30. .1942, Serial No. 467,402. Divided and this ap-' piication October 25,- 1943, Serial No. 507,599

11 Claims. (01. 106-153) This invention relates to methods of preparing commercially usable solutions and coating compositions of prolamines or prolamine-containing proteins directly from glutens, either com, wheat, barley, etc. It is particularly directed to such methods which will produce solutions and coating compositions of the alcoholvents to form the desired solutions. To isolate zein from corn gluten as a commercially usable powder is a laborious and expensive process, in-

volving steps of precipitation, settling, filtering,

washing and The solubility of the zein in zein solvents and the solution ch..racteristics suchas stability and gelling tendencies are largely dependent upon the care exercised in carrying out the steps'oi the process.

In accordance with the present invention I prepare solutions of zein or' zein-containing proteins directly from corn gluten under conditions that will readily produce awideyariety oi zein products in so far as properties and solubility characteristics are concerned, and thereby avoid the expense and objections incident to the preliminary isolation or zein in powder form.

In carrying out the present invention, corn gluten, for example, .in granular or powdered form, is treated with .a suitable solvent mixture, without the establishment oiap eeial conditions of hydrogen ion concentration either in the solvent or in the gluten,.- to extract the rein from the gluten. The solvent mixture comprises a base solvent having a boiling point above about 125 (2., preferably above about 150 C. and a diluent or extender having a boiling point below about 125 C. and, preierably, or about 100 C. and below. The base solvent is itself a solvent for zein and the diluent maybe, and preterably is. also a solvent for zein. The base solvents and diluents in accordance. with the present invention will be defined fully hereafter.

' soluble portion of corn gluten, of controlled sopreferably between about 140 to about 150 F., for a short period oi time generally not exceeding about three hours. It is preferred that the extraction time be not longer than about onehalf to about one hour since within this time and at the temperatures stated, the zein in the gluten is extracted and is not deleteriously affected.

The extract solution obtained as above described is now separated from the residual gluten by'filtration, pressing, centrifugal separation or in any other desirable manner and is distilled or otherwise treated to remove all or some of the diluent, as desired. It may be filtered preliminarily to the step of removing the diluent, if necessary. The resulting residue is a solution of zein or zein-containing protein in the base solvent alone with all of the diluent from the extract solution removed, or in .the base solvent and that portion of the diluent which has not been removed. The residual gluten, which still contains some protein, may be freed from re-i tained solvent by washing and recoveredior' further use as a cattle food or for other purposes.

The resulting zein or zein-containing solutions in accordance with the present invention, over a wide range of concentrations, are stable on standing at temperatures of 80 F. and below and do not-separate even when cooled to temperatures of to F. and somewhat below.

When cooled even to temperatures'as low as 10 above zero or to zero, solutions prepared in accordance with the present invention may separate and become solid: however, on heating again to temperatures of from about 45 to 70 F., a re-solution is eiiected, either without stirring or with slight stirring, and the solutions return to their normal. form at the reheating temperatures. Ingeneral, these solutions are substantially non-gelling and have but a slight tendency to increase in viscosity; that is, to

thicken or become heavier in body. In many instances they exhibit practically no tendency to thicken or to gel over practical periods of time in the order of about 3 to 6 months and even up to one 'year and longer. These solutions remain stable and reasonably constant in their characteristics" during the periods necessary for transportation and distribution, either in bulk or inpackages, or for storage for reasonable periods of time, and hence their field of ap- ,p licability is greatly increased.

The extraction is carried out at elevated temperatures, say from about to about lit,

In general, in the concentration of zein or other prolamine in commercially usable solutions 55 containing about 12 to 30% of protein, the

amount of base solvent necessary to obtain these concentrations in the final solutions is in and of itself insufllcient to give the proper relation between solvent and gluten ,for effective extraction results. If large amounts of the relatively high boiling point base solvents are used, suilleient to give the proper relation between solvent and gluten, the extraction results are not sumciently effective and, moreover, the cost ottreat ing the extracts to obtain the desired solids concentration is so prohibitive as to make this procedure commercially unfeasible.

The desired solvent to gluten ratio in accordance with the present invention is secured by adding to the desired amount of relatively high boiling point base solvent or mixture of base solvents one or more of the so-called relatively low boiling point diluent solvents. To obtain efiective extraction results, the solvent to gluten ratio should be in the order of about 2 to parts by weight of the former to about 1 part by weight of the latter. Due to the presence of a diluent or extender in the extracting solvent, the solvent to gluten ratio may be less than that which would be required with a base solvent alone and, notwithstanding the lower solvent to gluten ratio, the extraction results are generally more eilec- .tive. The diluent solvent or extender must have a lower boiling point and distillation range than the base solvent. It is preferred that these all-- uent solvents or extenders be of substantially lower boiling point and distillation range than the base solvent, as pointed out above.

Base solvents The base solvents are relatively high boiling compounds or mixtures of compounds as pointed out above and have asultable balance between the hydrocarbon constituents or radicals present in the solvent or solvent mixtures and the polar constituents or radicals present therein. A certain proportion of hydroxyl radicals in the base solvents is required to secure solvent action. Other polar radicals such as O (ether oxygen), Cl, NH: and COOH appear to aid or cooperate with the OH in securing the necessary conditions of polarity in the base solvents (in which term I include mixtures oi base solvents) ,for solvent action.

The proportion of polar radicals to hydrocarbon or non-polar radicals which I have found to be desirable lies within a range which extends between the limits oi! absolute methanol on the one hand, having 53% hydroxyl and 47% hydrocarbon radicals, and absolute ethanol on the other hand having 37% hydroxyl and 63% hydrocarbon radicals. The benzyl radical acts as it it were intermediate the methyl and ethyl radicals. This range is approximate and may vary somewhat depending on the solvent or solvent mixture used. The limits of this range are in-- dicative of solvent properties and provide a close and adequate guide to enable the operator, .by simple experimentation, to determine the required balance of polar and hydrocarbon radicals in the base solvent or mixture of base 501- vents in accordance with the present invention.

It may be stated that the base solvents in accordance with the present invention may be any one of the solvents or mixture of solvents described in my prior Patent No. 2,185,110 which has the required balance of polar and non-polar radicals, anda boiling point above about 125 C., preferably, above about 150 C. as pointed out above. For a more complete description of the kinds of solvents which may be used as base solvents in accordance with the present invention than is-disclosedherein, reference is made to the description of these solvents in my prior Patent No, 2,185,110.

Examples of base solvents in accordance with the present invention are the glycols such as diethylene glycol, propylene glycol, trlethylene glycol and mixtures thereof, including mixtures which contain ethylene glycol; diacetone alcohol: closed chain cyclic alcohols such as benzyl aicohol, cyclohexanol, iurfuryl alcohol, tetrahydrofurfuryl alcohol and mixtures of closed chain alcohols; glycol others such as ethylene glycol mono-methyl ether, diethylene glycol monomethyl ether, ethylene glycol mono-ethyl ether, diethylene glycol mono-ethyl and mixtures of glycol ethers; mixtures of two or more of the foregoing enumerated base solvents; mixtures of one or more of the foregoing base solvents with glycerine, or other solvents or mixtures of solvents, providing the mixture has the required polar to non-polar radical balance and the required relatively high boiling point. It is to be understood that the foregoing specifically mentioned solvents or mixtures of solvents is not intended tobe inclusive of all the base solvents which may be used in accordance with the present invention since they are merely set forth for illustrative purposes.

Diluent solvents The diluent solvents or extenders in accordance with the present invention may be, suitably, a single solvent or a solvent mixture which may or may notbe a solvent for zein or other prolamine, as desired. It is preferred, however, that the diluent or extender be a solvent for zein.

Thus, the extending. solvent may be one or more of the well-known alcoholic zein solvents such as anhydrous methanol, or constant boiling point mixtures (azeotropes) of aliphatic alcohols such as %-ethyl alcohol and 91% isopropyl alcohol. For convenience herein I term these alcoholic solvents "concentrated alcohol solvents. The

aqueous alcohol mixtures."

Another class of diluent solvents in accord-.

tures of an azeotropic concentrated alcohol solvent with a non-solvent and water. Examples of such diluents are mixtures of 95% ethyl alcohol or 91% lsopropyl alcohol with dichlorethylene, trichlorethylene, ethyl acetate, benzene, cyclohexane, etc., and water. Inthis class 01' d'iluent solvents I, also include non-aqueous azeo- -tropic mixtures of anhydrous methyl alcohol with hexane, cyclohexane, benzene, carbon tetrachloride, dichlorethylene, trichlorethylene, acetone, methyl acetate, ethylacetate, methyl ethyl ketone, etc. because one constituent of the mixture, methyl alcohol, is a zein solvent.

In addition to the foregoing, wherein at least one constituent of a diluent solvent mixture is a zein solvent, thediluent solvents may be suitable azeotropic mixtures. which are acid protein solvents wherein the individual constituents of the mixture are non-solvents for zein proteins. Thus, they may be azeotropic mixtures of water on the one hand and dioxan or butyl alcohol on the other. Dioxan forms with water a constant boiling point mixture containing 80% dioxan boiling at 86.9 C.; and butyl alcohol forms with water a constant boiling point mixture containing 63% butyl alcohol boiling at 92 C. They may also be suitable aqueous azeotiopic mix-' tures which are non-solvents for zein proteins such as ethyl methyl ketone and water. And they may also be non-aqueous azeotropic mixtures of anhydrous ethylalcohol or anhydrous isopropyl alcohol with hexane, cyclohexane, benzene, carbon tetrachloride, dichlorethylene, trichlorethylene, acetone, methyl acetate, ethyl acetate, methyl ethyl ketone, etc.

The diluents may also be suitable non-solvents of low polarity characterized by the presence of O, --Cl, NHz, COOH groups, etc. Examples of such diluents are dioxan, dichlorpentane, ethylene dichloride, dichlorethyl ether, etc. They may also be miscible hydrocarbons such as benzene, hydrogenated naphtha, etc. Or they may be suitable non-solvents of high polarity such as anhydrous ethanol, anhydrous isopropanol or water.

In general, extracting solvents consisting of or including the aqueous alcohol mixtures are capable of extracting larger amounts of zein protein from gluten than are the extracting solvents consisting of or including a concentrated alcohol solvent. It has been noted that for practical extraction procedures, using either a concentrated alcohol solvent alone or an aqueous alco- (apparent insolubility, for example) during the diluent and water removal which affect the solvent characteristics of the zein and zein-containing proteins in the base solvent utilized. These changes, where they take place, are not of a I permanent character and it is possible to effect such as methyl or ethyl alcohol or a mixture of such compounds.

In the preparation of usable solutions having a. wide field of applicability, I prefer that the removal of diluent and waterbe controlled so as to leave in the final solutions at least about 1 to 3% by weight of water or an equivalent hol mixture alone, approximately 2 /2 parts by a weight of solvent to l of gluten may be used. At this concentration, with gluten containing approximately 60% total protein, the extract solutions of the concentrated alcohol'solvent contain a maximum zein protein content of approximately 10% whereas the extract solutions of the aqueous alcohol mixture solvents contain a'maximum zein protein content of from about 12% to about 15% and even up to 20%. In addition, the aqueous alcohol mixture solvents are capable of extracting a substantially larger proportion of a desirable type of zein present in the protein of the gluten than are the concentrated alcohol sol vents.

Zein solutions-of a desired concentration and of a wide applicability can be obtained directly from gluten by having in the final solution as the only solvent or as the main solvent for zein, a relatively high boiling point solvent having the required balance of polar and non-polar radicals as described herein. It is now well established that the viscosity, gelling tendencies, and practical usability of zein solutions are in no small part dependent upon the character of the solvent in which the zein is dissolved.

Zein or zein-containing extract solutions containing any one or more of the foregoing base solvents in accordance with the present invention, may be boiled, distilled or otherwise treated to remove part or all of the diluent. It is evident that practically all 01' the diluent, including any water carried from the gluten to the extract solu-' tion, may be removed, thereby obtaining solutions of zein or zein-containing. proteins, in the base solvent which, for all'pralctical purposes, are substantially anhydrous. Such solutions vary widely in character, depending upon the choice of solvents or solvent mixtures used, as is to be amount of other highly hydroxyla ed compound, preferably water. Where this is not possible, water may be added to the final solution, in the amounts stated. While water is, in general, not

an essential constituent of some of the solutions formed in accordance with the present invention, the solutions are generally of an improved character when they contain small amounts of water. The solutions may contain larger amounts of water, say between 5 to 10%, or even more.

As already pointed out, the type or character of the zein-containing protein produced by the extraction is in no, small part dependent on the character of the extraction solvents used. This condition is particularly pronounced when the highly aqueous alcohols or the high water azeotropes'such as dioxan-water or n-butyl alcohol-water mixtures are used as diluents.v Not only do these diluents eflect the extraction of a larger amount of the zein-containing protein than do the more concentrated alcohols, but

having a high viscosity and pronounced colloidal consistency. On the other hand the zein pro-' tein produced with the concentrated alcohols; and less aqueous diluents tends to produce solutions having a lower viscosity and a lesser collcidal consistency. It is thus evident that various types of zein protein having substantially difi'erent properties can be produced by proper selection and composition of the diluents.

From the'"- foregoing it is manifest that the nature'and properties of the finished solution will be determined by the nature of the base solvent, the amount of zein protein present in the solution and the type or character of the zein protein extracted by the particular diluent used. It is apparent that with the solveritand diluent combinations possible, a wide variety of solutions for many use can be produced by the methods of the present invention.

Within the range of the many possible com binations and the methods in accordance with the present invention, solutions may be produced which require further adjustment or modification in order to secure improved solution or desired stability and controlled gelling properties. Such adjustments or modifications can be readily eifected by the use of rosin, fatty acids,'compatible amines such as monoethanolamine, triethanolamine, etc., amine soaps of rosin or fatty acids,v or by the various methods and materials for producing stable, controlled "gelling, zein solutions described in my issued Patents Nos. 2,185,122; 2,246,779 and 2,298,548.

tion.

In the following examples I disclose illustrative methods for producing zein or zein-containing solutions directly from gluten in accordance with the present invention. In the exampics and elsewhere throughout thespeciflcation,

the term parts" indicates parts by weight. w

Example 1.A solvent mixture containing '12 parts of anhydrous isopropyl alcohol (99%), 40

parts of diethylene gylcol and 8 parts of ethylene' glycol was added to 30 arts of powdered gluten in a vessel. The mixture was heated to about 160 F. and held at about that temperature for about /2 hour with stirring to extract the zein-containing proteins from the gluten.

The mixture was then forced through a filter to separate the zein-containing extract and the extract was then slowly heated to about 250 F. and held at about that temperature with stirring until cessation of visible boiling. The residue was a solution of zein-containing proteins principally in the mixture of glycols.

In the following examples the manipulative procedures were the same as those set forth in Example 1, with the exceptions hereinafter noted, and in each instance the extracts were heated until cessation of visible boiling.

Example 2.-A solvent mixturecontaining 72 Q parts-of anhydrous denatured. alcohol (Paco),

d0 parts of diethylene glycol and 8 parts of ethylene glycol was added to 30 parts of powdered gluten. The procedure was as in Example 1 and the resulting residue was a solution of zein-containing proteins principally in the mixture of glycols.

Example 3.A solvent mixture containing '72 parts of 91% isopropanol and 48 parts of a mixture consisting of 88.9% of propylene glycol and 11.1% of diethylene glycol monoethyl ether was added to 36 parts of powdered gluten. The procedure was as in Example 1 except that the extraction temperature was 180 F. The resulting residue was a solution of min-containing proteins principally in the glycol and glycol ether mixture.

Example 4.A solvent mixture containing so parts of denatured 95% alcohol (Paco). and to parts of a mixture consisting of 75% of diethylene glycol and 25% benzyl alcohol was added to as parts of powdered gluten. The

ethylene glycol and of ethylene glycol monoethyl ether was added to parts of powdered gluten. The procedure was as in Example 1 except that the extraction temperature was 140', I". The resulting residue was a solution of zein-containing proteins principally in the glycol and glycol ether mixture. 1

Example 7.-A solvent mixture containing 60 parts of a mixture consisting of 90% of 91% isopropane] and 10% or water, and parts of a mixture consisting of 75% of diethylene glycol and 25% of ethylene glycol monomethyl ether was added to 30 parts of powdered gluten. The procedure was as in Example 1 except that the extraction temperature was 140 F. The resulting residue was a solution of the min-containing proteins principally in the glycol and glycol ether mixture.

Example 8.A solvent mixture containing 60 parts of a mixture consisting of 80% of denatured 95% ethyl alcohol ("Paco") and 20% of water. and 40 parts of a mixture consisting of 75% of diethylene glycol and 25% of benzyl alcohol was added to 30 parts of powdered gluten. The procedure was as in Example 1 except that the extraction temperature was 140 F. The resulting residue was a solution of the zein-containing proteins principally in the glycol and benz'yl alcohol mixture. v

At the cessation of boiling as referred to in the examples some proportion of the lower boiling constituents of the diluent originally used remains in the final solution. The proportion thereof so remaining depends upon the iinaltempera ture and the boiling point curve of the mixture. Considerable proportions'of the diluent or of its constituents, including water. may remain without causing gelling of the final solution in reasonable periods of time. This is particularly true where the glycols are used. In this respect the final solutions show differences from solutions of commercial zein containing large amounts of water as in the prior art, apparently by reason of understood.

procedure was as in Example 1 except that the extraction temperature was 140 F. The resulting residue was a solution of zein-containing proteins principally in the diethylene glycol and benzyl alcohol mixture.

Example 5.-A solvent mixture containing parts of anhydrous synthetic methanol and 40 parts of a solvent mixture consisting of of diethylene glycol and 25% of ethylene 8111200] monoethyl ether was added to to parts of powdered gluten. The procedure was as in Example 1 except that the extraction temperature was 140 F. The resulting residue was a solution of the hem-containing proteins principally in the diethylene glycol and glycol ether mixture.

Example 6.-A solvent mixture containing 69 parts of a mixture consisting oi or denatured ethyl alcohol (Paco") and 20% of water,

to parts of a mixture consisting of 75% oi dimy In general and influenced by the type and amount of zein protein present, the solutions prepared as described above and the coating compositions prepared therefrom have the properties, particularly when heated, of being able to "give up their solvent or solvents readily, and when applied to any surface they quickly and readily form tough, flexible, non-tacky, hard and 8811-. erally transparent coatings even when retaining some solvent. The coatings formed by these sein- -containing solutions and coating compositions are very strong and have adherent properties. In these-solutions. and coating compositions the film forming properties thereof can be built up to produce films of great toughness, flexibility, hardness and gloss. Under normal temperature conditions, many of the zein-containing solutions or coating compositions. will produce non-blushing coatings on drying, without the aid of supplemeritary anti-blushing agents as in the prior art.

The coating compositions prepared from the above solutions may be modified and used as fully described in. the aforementioned application, Beria-l No. 467,402.

While my invention has been described in connection with certain specific examples, it is, of course, obvious it' is not to be construed as lim- 170 F." is not to be construed as a precise critical range, but, rather, as a range of temperatures indicative of the elevated temperature at which the extractions may be carried out.

I claim: I

1. The method of preparing directly from gluten a solution of zein-containing proteins in a mixture of solvents comprising as essential solvent constituents for the min-containing proteins, a mixture of solvents each having a boiling point above about 125 C. and having a pro-- portion of polar to non-polar radicals which lies within a range extending between the limits of the proportion of polar to non-polar radicals of methanol and the proportion of polar to nonpolar radicals of ethanol, which comprises contacting gluten with a solvent mixture at an elevated temperature in the order of about 120F'. to about 170 F. to extract zein-containing proteins from the gluten,.said solvent mixturecomprising the aforesaid zein-oontaining protein solventshaving boiling points above about 125 C.

and a miscible diluent therefor having a" boiling point below about 125 C., separating the extract from the residual gluten and removing at least part of the diluent from the extract to form the aforesaid solution.

2. The method of preparing directly from gluten-a solution of zein-containing proteins in a mixture of solvents comprising as essential solvent constituents ior the zein-containing proteins, a mixture of solvents each having a boiling point above about 150 C. and having a proportion of polar to non-polar radicals which lies withhi a range extending between the limits of.

from the residual gluten and removing at least p rt of the diluent from the extract to form the aforesaid solution.

'3. The method of preparing directly from gluten a solution of zein-containing proteins in a mixture of solvents comprising as essential solvent constituents for the zein-containing proteins, a mixture of solvents each having a boiling point above about 150 C. and having a proportion of polar to non-polar radicals which lies within a range extending between the limits of the proportion of polar to non-polar radicals of methanol and the proportion of polar to nonpolar radicals of ethanol, which comprises contacting gluten with a solvent mixture at an elevated temperature in the order of about 120 1''. to about 170 F., to. extract zein-containing proteins from the gluten, said solvent mixture comprising the aforesaid zein-ccntaining protein solvents having boiling points above about 150 C. and a miscible diluent therefor having a boiling point below about 125 C., separating the extract from the residual gluten and removing substantially all of the diluent from the extract to form the aforesaid solution.

4. The method of preparing directly from gluten a solution of zein-containing proteins in a mixture of solvents comprising as essential solvent constituents for the zein-containing proteins, a mixture of solvents each having a boiling point above about 150 C. and having a pro-,

portion of polar to non-polar radicals which lies within a' range extending between the limits of the proportion of polar to non-polar radicals of methanoland the proportion of polar to nonpolar radicals of ethanol, which comprises contacting gluten with a solvent mixture at an elevated temperature in the order of about F. to about 170 F. to extract zein-containing proteins from the gluten, said solvent mixture comprising the aforesaid zein-containing protein solvents having boiling points above about 150 C. and a miscible diluent therefor having a boiling point'below about 0., said diluent being a solvent for said zein-containing proteins, separating the extract from the residual gluten and removing at least part of the diluent from the extract to form the aforesaid solution.

5. The method of preparing directly from gluten a solution of zein-containing proteins in a mixture-of solvents comprising as essential solvent constituents for the zein-containing proteins, a mixture of solvents each having a boiling point above about C. and having a proportion of polar to non-polar radicals which lies within a range extending between the limits of teins from the gluten, said solvent mixture comprising the aforesaid zein-containing protein solvents having boiling points above about 150 C. and a miscible diluent therefor having a boiling point below about 100 C., said diluent being a substantially anhydrous solvent for said zeincontaining proteins, separating the extract from the residual gluten and removing at least part of the diluent from the extract to form the aforesaid solution.

6. The method of preparing directly from gluten a solution of zein-containing proteins in a mixture of solvents comprising as essential solvent constituents for the zein-containing proteins, a mixture of solvents each having a boiling point above about 150 C. and having a proportion of polar to non-polar radicals which, lies within a range extending between the limits of the proportion of polar tonon-polar radicals of methanol and the proportion of polar to nonpolar radicals of ethanol, which comprises contacting gluten with a solvent mixture at an elevated temperature in the order of about 120 F. toabove F. to extract zein-containing proteins from the gluten, said solvent mixture comprising the aforesaid zein-containing pro-v tein solvents having boiling points above about 150 C. and a miscible diluent therefor having a boiling point below about 125 C.,- said diluent being an aqueous solvent for said zein-containing proteins, separating the extract from the residual gluten and removing at least part of the diluent from the extract to form the aforesaid solution. I

7. The method of preparing directly from gluten a solution of zein-containing proteins in a mixture of solvents comprising a glycoland a glycol ether as essential solvent constituents for the zein-containing proteins, which comprises contacting gluten with a solvent mixture at an elevated temperature in the order of about 120 F. to about 170 F. to extract zein-containing proteins from the gluten, said solvent mixture comprising a glycol, a glycol ether and a miscible diluent therefor'having a boiling point below about 125 C separating the extract from the residual gluten and removing at least part of the diluent from the extract to form the aforesaid solution. V

8. The method of preparing directly from gluten a solution of zein-containing proteins'in a comprising a glycol, .a glycol ether and a miscible diluent therefor having a boiling point below about 125 (1., said diluent being an aqueous solvent for said zein-containing proteins. separati'ng'the extract from the residual gluten and removing at least part of the diluent from the extract to form the aforesaid solution. .10. The method oi! preparing directly from gluten a solution of zein-containing proteins in a mixture of solvents comprising propylene glycol and diethylene glycol monoethyl ether as essential solventconstituents tor the zein-containing mixture of solvents comprising a glycol and aglycol ether as essential solvent constituents for the zein-containing proteins, which comprises contacting gluten with a solvent mixture at-an elevated-temperature in the order of about 120 F. to about.l F. to extract zein-containin proteins from the gluten, said solvent mixture comprising a glycol, a gylcol ether and a miscible diluent therefor having a boiling point below about 125 C., said diluent being a solvent for said zein-containing proteins, separating the'extract from the residual gluten and removing at least part of the diluent from the extract to form the aforesaid solution.

9. The method of preparing directly from gludiethylene glycol monoethyl ether and 91%.iso-.

ten a solution of zein-containing proteins in a mixture of solvents comprising a 'glycol and a glycol ether as essential solvent constituents for the zein-containing proteins, which comprises contacting gluten with a solvent mixture, at an elevated temperature in the order 01' about it. about F. to extract zein-containing pro-'- teins from the gluten, said solvent mixture proteins, which comprises contacting gluten with elevated temperature in tract zein-containing proteins from the gluten, said solvent mixture comprising propylene glycol,

separating the extract from the and removing at least parto! the propyl alcohol, residual gluten isopropyl alcohol from the extract to form the aforesaid solution- 11. The methodoi preparing directly from gluten a solution of zein-containing proteins in a mixture of solvents comprising diethylene glycol and benzyl alcohol as essential solvent constituents forthe rein-containing proteins, which comprises contacting gluten with a solvent mixture at an elevatedtemperature in the order of about 120 F. to about 170 F. to'extract zein-containing proteins from the gluten, said solvent mixture comprising diethylene glycol, benzyl alcohol, 95% ethyl alcohol and water, separating the extract from the residual gluten and removingat least part of the.95% alcohol and water from the extract'to form the aforesaid solution;

ROY E. COLEMAN. 

